The production of P(AS) for a variety of industrial and commercial uses has been known for some time. P(AS) is moldable into various articles including, but not limited to, parts, films, and fibers by means of, for example, injection molding and extrusion molding techniques. These articles have utility in a variety of applications where heat and chemical resistance properties are desired. For example, P(AS) can be utilized as a material for preparing electrical and electronic parts and automotive parts.
Generally, P(AS) is prepared by contacting reactants comprising at least one halogenated aromatic compound, at least one polar organic compound, hereinafter referred to as POC, at least one sulfur source, and at least one base under polymerization reaction conditions. Molecular weight modifier compounds can be added to produce high molecular weight P(AS). The most preferred modifier compound is sodium acetate due to its availability and effectiveness.
There are several problems associated with the synthesis of high molecular weight P(AS) that can cause production expenses to be high. First, in a quench recovery P(AS) process, there is a 5% to 15% reduced feedstock conversion to P(AS) product due to the loss of low molecular weight P(AS) and cyclic and linear P(AS) oligomers in a waste stream called "slime". Typically, this waste stream often is disposed in landfills or other disposal facilities. Secondly, the modifier compound utilized to synthesize high molecular weight P(AS) often is used only once in a polymerization process and is not captured and recycled for subsequent use. This constitutes a great expense in P(AS) production due to higher feedstock and waste disposal costs. Thirdly, the POC utilized in the process can be recovered, but often at a high cost. For example, n-hexanol often is utilized to extract N-methyl-2-pyrrolidone, a common POC. Operating a hexanol extractor system can require handling as much as 30 to 40 pounds of n-hexanol per pound of P(AS) produced causing high equipment and operational costs.
This invention provides a P(AS) process which recovers low molecular weight P(AS) and cyclic and linear P(AS) oligomers for future use. In addition, this invention provides a method for recovering the modifier compound, which greatly reduces feedstock and disposal expenses compared to current P(AS) processes. This invention also provides a more efficient means to recover the POC utilized in the process. Finally, as a result of these improvements, the P(AS) produced by this invention has higher purity than that produced from current P(AS) processes.